NCCN Guidelines for Patients
Colon Cancer, Version 1.2014
Colon cancer basics
How colon cancer starts and spreads
muscularis mucosae. The epithelium absorbs water
from stool and makes mucus. Mucus helps move
stool through the colon. The lamina propria is a thin
layer of connective tissue. The muscularis mucosae is
a thin strip of muscle.
The second layer of the colon wall is called the
submucosa. It consists of connective tissue, blood
and lymph vessels, and nerve cells. Lymph is a
clear fluid that gives cells water and food. It also has
white blood cells that fight germs. Blood and lymph
drain from colon tissue into vessels that are in the
submucosa and then travel to other sites.
The third layer of the colon wall is called the
muscularis propria. It is mostly made of muscle fibers.
These muscles help move stool through the colon.
The fourth layer is the outer most part of the colon
wall. It consists either of adventitia or serosa.
Adventitia is connective tissue that binds the colon to
other structures. The serosa, also called the visceral
peritoneum, is a membrane. It has a thin layer of
connective tissue, called the subserosa, which is
covered by a single row of cells that make lubricating
fluid. This fluid allows the colon to move smoothly
against other organs.
How colon cancer starts
Cancer is a disease of cells—the building blocks
of tissue in the body. Almost all colon cancers are
adenocarcinomas. Adenocarcinomas are cancers that
start in cells that line glands and, in the case of colon
cancer, make mucus. Adenocarcinomas of the colon
are the focus of this book.
Inside of cells are coded instructions, called genes, for
building new cells and controlling how cells behave.
Changes in genes, called mutations, can cause
normal colon cells to become cancer cells. It is not
fully understood how genes change and cause cancer.
Colon cancer often starts in a polyp. A polyp is an
overgrowth of cells from the epithelium of the colon
wall. Not all polyps are the same. They all grow from
the mucosa, but they differ in size, shape, and how
their cells look. The chance of cancer forming in
polyps differs by the type of polyp. There are three
types of colon polyps.
• Adenomatous polyps, or adenomas, have
cells that don’t look like normal colon cells.
They are the most common type of polyp.
Most do not become cancer, but most polyps
with cancer started as adenomas.
• Hyperplastic polyps have cells that grow fast.
They are often found in the last part of the
colon and in the rectum. They rarely become
• Inflammatory polyps often grow after a flare-
up of an inflammatory bowel disease. They
can have any shape. The chance of them
becoming cancer is low.